JPH10120836A - Silicone-modified low-density polyethylene and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a modified polyethylene compsn. improved in hydrophobicity by compounding a linear low-density polyethylene with a specific mutually acting diorganopolysiloxane. SOLUTION: This compsn. contains 100 pts.wt. linear low-density polyethylene (A) and at least 1 pt.wt. mutually acting diorganopolysiloxane (B) having a number average mol.wt. of at least 38,000. Examples of ingredient A are low- density polyethylene, a substantially linear ethylene homopolymer, and a substantially linear ethylene/3-10C α-olefin copolymer. Ingredient B has at least one mutually acting group (e.g. a hydroxyl, amino, or alkenyl group) in the molecule, the most favorable group being hydroxyl. This compsn. is prepd. pref. via a masterbatch contg. up to 50 pts.wt. ingredient B and finally contains 1-5 pts.wt. ingredient B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION This invention relates to modified hydrophobic modified polyethylene compositions wherein a small amount of interactive diorganopolysiloxane is added to the polyethylene resin.

[0002]

The present invention is a composition comprising the following (A) and (B): (A) 100 parts by weight of a low density polyethylene resin; and (B) a number average molecular weight of 1 part by weight or more. At least 38,
000 interactive diorganopolysiloxanes.

[0003] In a preferred embodiment, the linear low density polyethylene is modified with a hydroxy-functional diorganopolysiloxane. Such compositions exhibit surprising hydrophobicity.

[0004] Low density polyethylene (A) is prepared from low density polyethylene (LDPE) and a substantially linear ethylene homopolymer / interpolymer of ethylene and an α-olefin having 3 to 10 carbon atoms. Such as linear low density polyethylene (LLDPE). Typically, these systems density 0.85~0.97g / cm ^3, more preferably 0.8
In 75~0.930g / cm ^3, a weight average molecular weight (Mw) of
Is from 60,000 to 200,000. These polymers are well known in the art and need not be described further.

The diorganopolysiloxane (B) of the present invention
Has a number average molecular weight (Mn) of at least about 38,000
But preferably less than about 1,000,000. Preferably, the Mn of (B) is from 38,000 to 45
000, more preferably 75,000 to 450,0
00.

[0006] It is believed that many of the compositions of the present invention can be processed with conventional extrusion or injection molding equipment.
When these compositions are extruded, the molecular weight of component (B) will affect the processing properties of the composition.
When the Mn is less than 38,000, the composition will exhibit excessive screw slip, for example, less revolutions per minute (RP) than would be expected for a given extruder.
M). Furthermore, at lower molecular weights, the extruder output is significantly reduced when the composition is extruded a second time. Such a second extrusion is often necessary in industrial operations. For example, errors in manufacturing, such as inaccurate extruder settings, or exclusion / quantitative insufficiency of key components, may require re-extrusion of "off-spec" material. Similarly, in the inflation operation, the ends of the flattened bubbles are trimmed and recycled to the extruder. Further, when the scrap is returned and recycled, re-extrusion is performed, a process which is described in the art as "post-consumer recycling (post-consumer recycling).
-Consumer cycle). On the other hand, if Mn exceeds 1,000,000, mixing diorganopolysiloxanes into polyethylene becomes difficult, even if such siloxanes can be used.

[0007] Also important to the practice of the present invention is that
Die type used in the extrusion process of the present invention. The compositions often need to be extruded or injected through a metal die. The preferred die is stainless steel, but chrome, nickel or platinum dies can also be used. The metal need not be solid chromium or platinum since the die may be plated. The die attracts the interactive groups of the polydiorganosiloxane and transfers the polydiorganosiloxane to the die. As a result, the polydiorganosiloxane collects and concentrates on the surface of the film, giving the film improved hydrophobicity.

The component (B) has a Mn of 100,000 to
1,000,000, most preferably 250,000-
A gum in the range of 350,000. Component (B)
May be a linear or branched polymer in which the organic group is independently selected from a methyl group or a phenyl group.

Suitable diorganopolysiloxanes are polydimethylsiloxane homopolymers, copolymers consisting essentially of dimethylsiloxane and methylphenylsiloxane units, copolymers consisting essentially of dimethylsiloxane and diphenylsiloxane units, diphenylsiloxane units and Includes copolymers consisting essentially of methylphenylsiloxane units and homopolymers of methylphenylsiloxane units. Mixtures of two or more such polymers or copolymers can also be used as component (B).

For the purposes of the present invention, the diorganopolysiloxane (B) must contain at least one, preferably two or more, interactive groups in the molecule, for example hydroxyl, amine or alkenyl groups. Must. The term "interactive" refers to the tendency of this group to be attracted to the surface of the metal, for example, an extrusion die. Most preferred are hydroxyl groups. The interactive group may be at the end of the molecule, along the chain, or at both positions. Preferably, this interactive group is present at the end of the chain, as in the case of hydroxyl groups, and in the form of diorganohydroxysiloxy groups such as dimethylhydroxysiloxy, diphenylhydroxysiloxy and methylphenylhydroxysiloxy. When this interactive group is present only along the chain, the end group of the diorganopolysiloxane is terminated by a non-reactive component, typically a di- or triorganosiloxy species such as dimethylvinylsiloxy or trimethylsiloxy. May be.

The diorganopolysiloxane (B) is preferably a linear polydimethylsiloxane containing up to 50 mol% of phenyl groups. Most preferably, it is a polydimethylsiloxane homopolymer having dimethylhydroxysiloxy end groups.

The composition of the present invention comprises at least 1 part by weight of diorganopolysiloxane (B) and 100 parts by weight of LD.
It is prepared by sufficiently dispersing in PE (A). For masterbatches, the composition according to the invention may comprise up to 50 parts by weight of component (B). For the final product, 1 to 5 parts by weight of component (B) is used per 100 parts by weight of component (A). More preferably, 1 to 4 parts by weight of component (B) per 100 parts by weight of (A), most preferably 1 to 3 parts by weight of component (B) is used. (A) 100
When the diorganopolysiloxane is added in an amount of less than 1.0 part per part by weight, especially at high speed extrusion,
There is little improvement in the contact angle over the corresponding unmodified polyolefin. Similarly, if (B) is more than 10 parts per 100 parts by weight of (A), the surface quality of the extruded material starts to deteriorate. Furthermore, if (B) is used in excess of 10 parts per 100 parts by weight of (A), an excess of siloxane is observed on the surface of the extrudate, which adversely affects properties such as printability and sealability. give. in addition,
The physical properties of the final extrudate deteriorate. Thus, the preferred composition range provides good contact angles, hydrophobicity, and low screw slip during processing, especially at high extruder output speeds.

[0013] The dispersion of the diorganopolysiloxane (B) in the polyethylene (A) can usually be achieved by any of the conventional methods of mixing additives into thermoplastics at elevated temperatures. For example, the two components can be blended in a twin screw extruder, with or without a mixing head, a Banbury mixer, a two-roll mill, or a single screw extruder. The equipment used to mix these components is not particularly limited as long as a uniform dispersion of (B) in (A) is achieved. Preferably, the dispersed particle size is 10 μm or less.

In addition to the above components, the composition of the present invention may contain up to 1% by weight of each of the following: filler, hardener, lubricant, U.S.P. V. Stabilizers, antioxidants, catalyst stabilizers and other processing aids commonly used to modify polyolefins. The use of more than 1 wt% of any of these additives will hinder the purpose of the present invention, for example, resulting in sub-optimal processing and / or resulting extrudate properties. This is especially important in the case of the production of blown films, where good surface quality is very important. Furthermore,
Up to 15 wt% of the total composition of the present invention may contain an anti-blocking agent.

Specific examples of such additives include, but are not limited to, the following: Diatomaceous earth, octadecyl-
3- (3,5-di-5-butyl 4-hydroxyphenyl) -propionate, bis (2-hydroxyethyl)
Tallow amine, calcium stearate, 2,4,6-
Trichloro-1,3,5-triazine and 2,4,4-
Polymer of N, N-bis (2,2,6,6-tetramethyl-4-piperidinyl) -1,6-hexanediamine having trimethyl 1,2-pentaamine, 2,2
Polymer with dimethyl succinate having 6,6-tetramethyl-1-piperidineethanol, 2,2-thiobis [4-tert-butylphenolate] n-butylamine nickel, tris (2,4-di-tert-butyl) Phenyl) phosphite, bis (2,4-di-t-butylphenyl) pentaerythritol diphosphite, trisnonylphenyl phosphite, polyethylene glycol, erucamide, titanium dioxide, alumina, hydrated alumina, talc, 2-hydroxy- 4-n-octyloxy benzophenone, silicon dioxide, zinc oxide, zinc sulfide and zinc stearate.

According to the present invention, the diorganopolysiloxane (B) is added to a low-density polyethylene resin (A), and this resin is extruded at a high temperature to form a molded article (for example,
Cylindrical / cylindrical sections, such as films, ribbons,
(Rods, rings, fibers, sheets, etc.). The extrudate obtained has improved hydrophobicity compared to the extrudate without diorganopolysiloxane (B). This method is particularly applicable to the production of cast or blown films, but is also useful for extrusion blow molding; injection molding; pipe, wire or cable extrusion; fiber production; and high shear melt processing of all polyolefin resins. It is.

Briefly, blown films are typically made by a "bubble" process, in which the polyolefin composition (ie, melt) is extruded through an annular die to form a film in the form of a bubble. The bubble is withdrawn from the die at a speed greater than the extrusion speed while positive air pressure is maintained within the bubble. Films produced in this manner are biaxially oriented as a result of being stretched radially and axially, which orientation generally gives the films improved mechanical properties. Cast films are generally prepared by extruding a polyolefin through a slot die and then cooling on one or more chill rolls. When this composition is injection molded, the die must also be metal, or the mold from which the thermoplastic is injected must be plated with a metal, such as stainless steel, or especially chromium, nickel or platinum. Must.

The compositions of the present invention may be prepared by other process steps known in the art, such as injection molding, injection blow molding,
It can be provided for extrusion blow molding, inflation method, cast film method, profile extrusion, rotation molding, compression molding, transfer molding, thermoforming and calendering.

While it is possible to obtain a relatively uniform dispersion by injecting component (B) into the screw section of the extruder while feeding polyethylene pellets through its hopper, component (B) is first added. It is preferable to form a master batch by sufficiently dispersing in a part of the component (A). The masterbatch (or concentrate) containing 1 to 50 wt%, preferably 20 to 50 wt% diorganopolysiloxane, is milled or pelletized and the remaining particles are dry blended with additional polyethylene (matrix) and then dried. The blend may be extruded to form a suitable composition of the present invention. Use of this masterbatch method results in a more uniform dispersion of the diorganopolysiloxane within the polyethylene matrix.

The polyethylene used to prepare the masterbatch may be the same or different from the matrix polyethylene resin. Preferably, the two are of the same general type (ie, the same polyethylene in the masterbatch and the matrix). However, in a highly preferred embodiment of the present invention when the matrix polyethylene is LLDPE, it has been found that further addition of a two-component system is beneficial.

Thus, a highly preferred composition of the present invention comprises 100 parts by weight of LLDPE and 1 to 10 parts by weight of a diorganopolysiloxane. These compositions are LD
It may contain PE. However, whether LDPE is added to the composition depends on how the composition is processed. When this film is watched, those skilled in the art will appreciate that the composition of thermoplastic resin component (A) 10
We know that only wt% can be LDPE. 1
An amount greater than 0 wt% will cause difficult problems during the blown process. However, if the resin is a cast film, these resins will not appear and any amount of polyethylene component (A) may be used. When used in the inflation process, less than 1 part by weight of L per 100 parts by weight of LLDPE of the ternary composition
DPE is generally indistinguishable from systems containing only components (A) and (B). In a specific example in which the film is expanded, a preferable ratio is 0.1 to 5 parts by weight of LDPE (C) per 100 parts by weight of LLDPE (A), and a preferable content of diorganopolysiloxane (B) is as described above. It is.

For the present invention, LDPE (C) has a number average molecular weight of up to 4,000,000 and a density of 0.915-0.
Any of 925 g / cm ³ of highly branched polyethylene homopolymer may be used.

The modified thermoplastic resin of the present invention has various improved properties. For example, the inventors believe that the silicone migrates to the surface of the thermoplastic resin, and this migration imparts improved properties to the surface, such as improved hydrophobicity and castability. Thus, films and molded articles, such as bottles or containers, made from the present invention have better hydrophobicity and / or castability.

Furthermore, the aggregation of the silicone on the surface of the thermoplastic gives the thermoplastic an improved "hand". In addition, the addition of the polyorganosiloxane of the present invention improves the process efficiency of this thermoplastic.

[0025]

The following examples are provided in the claims to further illustrate the invention, which is more fully defined. Unless otherwise indicated, all parts and percentages in these examples are by weight and all measurements were obtained at 25 ° C.

The contact angle between one drop of the specified liquid and the specified substrate was measured using a goniometer. The goniometer measures the angle of side contact of the drop with the substrate. The substance to be tested can be this liquid or a substrate. In these examples, distilled water was used and the substrate was varied by adding different siloxanes or different amounts of siloxane. The angle observed is reported in degrees along with what both the liquid and the substrate are. This method is called AS
Same as TM D 724.

For the measurements, the goniometer optical bench was leveled. A specific substrate was placed on a support and fixed. The platform was adjusted so that the substrate or film could be clearly seen through a microscope or video camera. By bringing the liquid directly into contact with the surface,
One drop (2.5 mm diameter) was placed on the substrate. This liquid did not drop on the surface. Otherwise, it would have been distorted while placed. Lighting is adjusted to the optimal level,
The microscope was focused on the silhouette of the dark drops against a relatively light background. The contact angles of both the left and right hand solid / liquid interfaces on the drop were measured. Report this. This procedure is repeated three times and the average is reported to the nearest degree.

In the examples, the following substances were used:

LLDPE = linear low density polyethylene; having a density of 0.917 g / cc, Dow Chemical
l Co. , The trademark DOWLEX ^™ 204 by MI
Octene-based copolymer of ethylene sold under 5A.

LDPE = also Dow Chemica
l Co. By DOW ^™ GP-LDPE 500
Low density polyethylene with a density of 0.923 g / cc sold as 4IM.

Example 1 A masterbatch of the siloxanes described below mixed in the above polyethylenes was prepared by thoroughly mixing these components with the polyethylene at elevated temperature. This polyethylene is 100% LD
PE. A sufficient amount of silicone was added to make a masterbatch in which the silicone was 25 wt% of the resulting LLDPE composition.

Silicone A has a Mn of 400,000,
It is an OH-terminated polydimethylsiloxane having a viscosity at 25 ° C. of 2.5 × 10 ⁷ mPa · s (cp).

Silicone B is an OH-terminated polydimethylsiloxane having a Mn of 65,000 and a viscosity of 60,000 mPa · s (cp).

Silicone C is an OH-terminated polydimethylsiloxane having a Mn of 38,000 and a viscosity of 10,000 mPa · s (cp).

Silicone D has a Mn of 400,000,
It is a vinyl-terminated polydimethylsiloxane having a viscosity of 2.5 × 10 ⁷ mPa · s (cp).

A plurality of specific masterbatches (MB) are
L / D (length / diameter) is 40/1 and screw diameter is 1
Haake Rheoc equipped with an 8 mm Leister ^™ Micro 18 co-rotating twin screw extruder
ord ^™ 90 system twin screw extruder (Haa
ke Corporation-Paramus, Ne
w Jersey). 8 in each room of this extruder
The temperature of each of the three zones was adjusted to 185 ° C. In each case, the MB composition was extruded through a strand die and chopped into pellets when cooled in a water bath.

The MB was used as a processing aid for polyethylene, which was well dispersed in an LLDPE matrix. The amount of pellets used was calculated to give a total silicone concentration of 1 wt% and 2.5 wt% of the thermoplastic resin for each of the four silicone resins used.

The thermoplastic silicone pellets and polyethylene were placed in eight zones of the extruder at 185 zones.
With the Haake twin screw extruder set at
By mixing again at a high temperature, it was fully blended. In each case, the masterbatch composition was extruded through a strand die and chopped into pellets when cooled in a water bath. This polyethylene was a 50/50 blend of LLDPE and LDPE.

After compounding in a twin screw extruder,
These pellets are blown into a blown film extruder (Davis Standard ^™ ) model KL-07 having an L / D of 24/1 and three heating zones at 220 ° C.
5 1.90 cm (3/4 inch) floor model (Flo
or model) extruder. Bubbles were made using a 2.5 inch diameter annular stainless steel die maintained at 220 ° C. The pressure inside the bubble was set so that the inflation ratio was 2, thus creating a 12.7 cm (5 inch) "inflated" tube film. The air ring used room air to blow around the bubbles to cool and crystallize the film. The film was gathered in a folding gate and pinch roll system. A sample was taken to measure the contact angle.

Table 1 below shows that the selected silicones improved the contact angle of the substrate, indicating a higher level of hydrophobicity than the standard control for unmodified polyethylene.

[0041]

As seen above, the addition of a functionally terminated silicone to LDPE improves hydrophobicity by 1-10%.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor David Joseph Romenesco United States, Michigan 48642, Midland, Elm Court 4102

Claims (6)

[Claims] 1. A composition comprising the following (A) and (B): (A) 100 parts by weight of a low density polyethylene resin; and (B) 1 to 50 parts by weight having a number average molecular weight of 38,000 to
1,000,000 interreactive diorganopolysiloxanes. 2. The composition of claim 1 wherein said resin (A) is a linear low density polyethylene resin. 3. The diorganopolysiloxane (B)
Is a polydimethylsiloxane having at least one pendant or terminal interactive group selected from the group consisting of a hydroxyl group, an amine group and an alkenyl group. 4. The composition according to claim 1, further comprising (C): (C) 0.01 to 100 parts by weight of a low-density polyethylene. 5. A method for producing a low-density polyethylene resin in which a processing aid is added to a polyethylene resin, wherein the processing aid is the composition according to any one of claims 1 to 4, further comprising: A method of manufacturing, wherein the composition and the polyethylene resin are passed through a metal die, whereby the processed resin exhibits improved hydrophobicity as compared to the unmodified resin. 6. The processed resin is formed by injection molding, injection blow molding, extrusion blow molding, inflation method, cast film method, profile extrusion, rotation molding, compression molding, transfer molding, thermoforming and calender molding. 6. The method of claim 5, which is subjected to a selected further process step selected from the group.